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Short (24-hour to 3-day) fasts

Intermittent fasting is the latest and greatest fad in the American weight loss scene.  I see more books and articles out about fasting every week. Some will say that it’s the solution to all your woes, but it is important to realize that it’s just another tool among hundreds. 

Intermittent fasting means either doing short fasts of one to three days often, as in once a week or month respectively, or fasting for more than sixteen to eighteen hours every day.  Time restriction is when you fast for 10-16 hours a day, and keep your eating to a 14 or less hour window. Fasting can be a good way to kick start a new healthy eating habit, or an additional trick for someone who eats healthy but is still trying to improve their health.

The origins of short or intermittent fasting periods date back antiquity.  References to fasting can be found in the Bible, the Koran, and in ancient Greek texts by Hippocrates, the father of medicine.  People have fasted for religious observance and as a therapeutic way to rejuvenate the body.  Plato and Socrates were both known to have fasted for days at a time to attain mental and physical efficiency.  Fasting has long been observed among animals during times of illness, and the use of fasting to treat illness among humans has been employed for centuries.

Fasting is done to increase the healing process of the body by decreasing the energy used to metabolize foods.  Fasting should ideally be done when you have the opportunity for rest, do gentle exercise, and do other self-care activities such as meditation or journaling.  Moderate to heavy exercise is not encouraged when fasting and can impair elimination.  Remember the more rest, the better the results.  Your energy can be directed towards healing, instead of other bodily functions. During a fast of greater than 16 hours, your body will clean up older cells and hormones that aren’t working as effectively any longer and makes new cells and hormones. It also decreases inflammation. 2 In a nutshell, fasting is a reset or refresh.

Intermittent fasting is one of the most nutritionally effective ways to live longer.1   Not only has fasting been proven in numerous laboratory trials to extend life expectancy but it has also been shown to reduce inflammation and risk of cancer or diabetes was well as change fat metabolism.2,3,4  Fasting could help you live healthier for a longer period of time when done right. 

Only water should be taken during a fast; filtered or spring water is best.  Some experts recommend juice, however, this is not considered true fasting.  Juice fasts are actually an elimination diet as nutrients are being ingested.   The quantity of water should be dictated by thirst, but you need to drink several glasses each day.  For hydration purposes the recommendation is typically ½ of your body weight in ounces of water daily at a minimum.   Losing vitamins or minerals is not usually of concern in a short fast of one to three days.  Some people add a little bit of sea salt or some electrolytes to their water (I add a quarter of teaspoon of salt to my first glass of lemon water every morning).  Humans have adapted biochemical mechanisms to exist for long periods without food.

The trick to fasting, whether you restrict calories for the better part of a day (which is called time restricted eating), a full day, or multiple days is to not overeat when you break the fast.  If you gorge yourself on food after not eating for a day you will have reaped no benefits.   The benefit from fasting is due to the overall caloric restriction over time and having your body switch from glucose to ketosis for fuel during your fast which helps decrease insulin resistance.  To break a fast you want to ensure you are consuming a small meal and not more than you would have normally eaten if you hadn’t fasted.  If you have fasted for two days or more than fruit is the food most often recommended to break a fast, that meal is typically followed by a meal of cooked vegetables, and then a meal of your regular healthy foods in an appropriate portion size.  Eat when hungry and stop when no longer hungry; that takes most people about 20 minutes to realize.     

Another trick is to ensure your fasts are truly intermittent.  If you fast for 18 hours every day on a time restriction diet, then your body will eventually adjust to that new norm.  To keep your metabolism firing at a high level, mix it up.  Fast for 12 hours one day, 18-20 the next and keep mixing it up.  One time skip breakfast, the next time eat dinner in the afternoon, it’s okay to go to bed hungry 😊

It is important to realize that fasting is only one part of a total health optimization program and not a panacea.  Fresh air, rest, exercise, sunshine, pure water, and wholesome high quality unprocessed food are all equally important to maintain a long healthy life.


  1. A fasting-responsive signaling pathway that extends life span in C. elegans, Uno et al., Cell Rep, 2013, Jan 31;3(1):79-91
  2. Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects, Feris et al., Nutr Res, 2012 Dec;32(12):947-55
  3. Intermittent fasting modulation of the diabetic syndrome in sand rats. II. In vivo investigations, Belkacemi et al., Int J Mol Med., 2010 Nov;26(5):759-65
  4. Influence of intermittent fasting and high-fat diet on morphological changes of the digestive system and on changes of lipid metabolism in the laboratory mouse, Krízová et al., Physiol Res, 1996;45(2):145-51
  5. Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women, Klempel et al., Nutr J, 2012 Nov 21;11:98

Erin Williams, MSN CN LMP, is the founder of, a health and wellness company established in 2001. Erin has a bachelor’s degree in Chemistry from Purdue, a master’s degree in Nutrition from Bastyr University, and is currently studying to become a Functional Medicine Practitioner. Erin enjoys sharing her love of natural health and wellness with people through lectures, blogs, and consultations.

Post Author: EZBalanceWellness